Re: [Xen-users] Xen hard-disk performance regression?

[Fabiano Francesconi <fabiano.francesconi@xxxxxxxxx>]

On Mon, Apr 12, 2010 at 02:10:45PM +0300, Pasi Kärkkäinen wrote:
> On Mon, Apr 12, 2010 at 10:47:59AM +0200, Fabiano Francesconi wrote:
> > On Mon, Apr 12, 2010 at 01:41:19AM +0200, Olivier B. wrote:
> > > On 12/04/2010 01:29, Fabiano Francesconi wrote:
> > > > I've tried with a (almost) vanilla kernel (only gentoo patchsets).
> > > >
> > > > I have the same issue so, I guess, it's a kernel misconfiguration /
> > > > kernel regression but it must be something wrong upstream too.
> > > >
> > > > Since I've been sharing with you my whole anamnesi, any of you has any
> > > > clue?
> > > >    
> > > 
> > > Can you try some more synthetics tests, with "dd" ?|
> > > latency on writes : dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k 
> > > count=10000
> > > write speed :|| dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k 
> > > count=128000
> > > read speed : ||dd if=/dev/sda of=/dev/null bs=4k count=128000||| (this 
> > > one will be greatly affected by cache)
> > > 
> > > And can you try with differents FS, ext3 and ext4 for example ?
> > > 
> > > Olivier
> > 
> > 
> > I've ran the test you pointed me out. The results are interesting
> > althought I haven't found an explanation for such a behaviour.
> > 
> > The dsync transfer ration is more than a minute slower on .32 kernel.
> > The same for fdatasync.
> > 
> > This for what concerns the root hard-disk (that's *not* the one I've
> > been talking since now).
> > 
> > The storage hard-drive, instead, shows that dsync transfer is _very_
> > faster on .32, but fdatasync isn't.
> > 
> > These results are very strange.
> > 
> > You'll find both log file attached here. I made them in a way you can
> > easily (vim)diff those.
> > 
> 
> How about oflag=direct transfers with dd? 
> 
> Are both kernels based on the novell/sles/opensuse patches? 
> 
> -- Pasi
> 

Here's the output of `time dd oflag=direct if=/dev/zero of=TESTFILE bs=4k 
count=10000`:

2.6.29-xen-r4:
10000+0 records in
10000+0 records out
40960000 bytes (41 MB) copied, 150,401 s, 272 kB/s

real    2m30.407s
user    0m0.009s
sys     0m0.226s


2.6.32-xen-r1:

10000+0 records in
10000+0 records out
40960000 bytes (41 MB) copied, 150,063 s, 273 kB/s

real    2m30.097s
user    0m0.005s
sys     0m0.170s

==

Same timings? Mhm.. interesting.. (althought those seem quite slowy)

Both kernels use the patchset provided by 
http://code.google.com/p/gentoo-xen-kernel/downloads/list .
If I remember correctly, the .29 patchset was provided by opensuse.
The .32 uses the patchset from SLE11 as reported in the link above.
-- 
Fabiano Francesconi [GPG key: 0x81E53461]

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